In a digital communication system, multipath fading caused by a transmission signal reflected from buildings or the like and Doppler shift caused by movement of a terminal device cause frequency selective fading and time variability of a transmission path. In such a multipath environment, a received signal becomes a signal in which a transmitted symbol and a symbol that arrives after a lapse of a delay time interfere with each other.
For the frequency-selective transmission path as described above, a Single Carrier (SC) block transmission system intended for obtaining optimum reception characteristics has been recently drawn attention (see, for example, Non-patent Literature 1). The SC block transmission system can reduce a peak electric power as compared to an Orthogonal Frequency Division Multiplexing (OFDM) transmission system that belongs to Multiple Carrier (MC) block transmission (see, for example, Non-patent Literature 2).
For example, a transmitter that performs SC block transmission generates a Phase Shift Keying (PSK) signal or a Quadrature Amplitude Modulation (QAM) signal that is a digital modulation signal, then transforms this signal to a time-domain signal, and thereafter adds a Cyclic Prefix (CP) to the time-domain signal for the purpose of multipath fading compensation. In general, a transmitter performing SC block transmission carries out Discrete Courier Transform (DFT) processing in a precoder in order to minimize a transmission peak power.
The SC block transmission described in Non-patent Literatures 1 and 2 can minimize the transmission peak power while reducing the influence of multipath fading. However, in the SC block transmission, since the phase and amplitude between SC blocks are discontinuous, an out-of-band spectrum is caused. The out-of-band spectrum is also referred to as “out-of-band leakage power”, and causes interference with adjacent channels. It is thus necessary to suppress the out-of-band spectrum. In a general communication system, a spectral mask is determined, and the out-of-band spectrum needs to be reduced so as to satisfy the spectral mask. To solve the problems as described above, Non-patent Literature 3 proposes a technique to insert static symbols into both ends of an SC block to thereby suppress the out-of-band spectrum. A transmitter described in Non-patent Literature 3 generates a data symbol and a static sequence that is a sequence of static symbols for each block, and multiplexes these symbols in a time domain, thereby generating an SC block having ends into which the static symbols are inserted.